Ecoregional Assessment of Biological Diversity in East Kalimantan

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East Kalimantan Ecoregional Assessment: Chapter 2 – Target Ecological Systems molesta and Eichhornia crassipes, Mimosa pigra and Polygonum barbatum). The first three species dominate the larger Semayang, Jempang and Melintang lakes, while P. barbatum dominates Perian Lake. Total plant coverage in the Mahakam Lakes varied between 15 % - 90 %. Lake Tawar, with a surface area of 10.3 ha, was most densely covered by water hyacinth (90%) - this lake is now very difficult to enter because this plant blocks its inlet. Most floating plants are regularly flushed out of the lakes during heavy rains and enter the Mahakam River. Unna Chokkalingam (pers. com.) stated that the Mahakam Lakes frequently silt up and river channels expand and change coarse remarkably. In dry periods, large parts of them are exposed and people plant rice in their centers. They also cut branches and place them over parts of the lake to “shade-fish”; this is said to greatly enhance the catch success for the fishermen. Conservation of these lakes is just as dependent on protecting the upper catchment areas where so much of the soil erosion and sedimentation comes from, as it is restoration and protection of the lakes themselves. Danielle Kreb (pers. com.) observed that the high density of gillnets used in Lake Semayang and Lake Melintang causes physical obstruction to the movement of Pesut, thereby reducing available habitat for this critically endangered dolphin species. This threat, together with high sedimentation caused by devegetation of the surrounding shorelines, has probably resulted in the elimination of these lakes as primary habitat for Pesut, as reported by Tas'an and Leatherwood (1984). Pesut occasionally move into the southern central waters of Lake Samayang. The impression is that this lake and the other Mahakam lakes are not particularly important for the Pesut, which is found elsewhere along the coast of Kalimantan. However, without more information on the ecology or their specific use of the lakes it would be premature to dismiss the importance of these lakes. It is possible for example; that births occur in the calmer waters of the lakes and that these areas are in fact very important in the life histories of the Pesut- even if only for short periods of their life cycles. [See section below entitled “Pesut Conservation Issues” for additional information.] Gönner (2000) states that the Middle Mahakam Area remains a crucial breeding and migration site for many bird species. Between 1988 and 1999, he reports a total of 90 bird species around Lake Jempang, including important breeding populations of various herons and the Lesser Adjutant (Leptoptilos javanicus). He also recorded what appears to be the first breeding record in Borneo of the Little Tern (Sterna albifrons). He states that, despite the enormous damage of recent forest fires, most of the 90 species of birds were found in the swamps and waterways of the Middle Mahakam area, including 12 heron species, 2 stork species, 2 duck species, 6 crake/rail species, 23 wader species and 4 tern species The appearance of visiting wading birds during the autumn migration depends on the water level of the Mahakam lakes. Significant numbers (mainly of Wood Sandpipers Tringa glareola) were only observed in extremely dry years (1993 and 1997), when the lakes had virtually disappeared. Vast mudflats and grasslands provided excellent feeding habitats for plovers, sandpipers and stilts. The shallow lakes also attracted large numbers of Whiskered 51
East Kalimantan Ecoregional Assessment: Chapter 2 – Target Ecological Systems Tern (Chlidonias hybridus) and Little Terns (Sterna albifrons) as well as herons (mainly Javan Pond Herons (Ardeola speciosa), Great Egrets (Egretta alba) and Purple Herons (Ardea purpurea), which fed on dying fish. Whiskered Terns, both of northern (C.h.hybridus) and austral (C.h.javanicus) origin, visited the Middle Mahakam Area in large numbers for feeding during migration time, and (in smaller numbers) for wintering. Goenner (2002) also recorded a large number of bird species (31) in the freshwater swamp forests directly adjacent to Lake Jempang. He states that the open water bodies were mainly used by raptors (6 species), terns (4 species) and 2 duck species. Cox et al. (1993) reported that endangered mammals such as Proboscis Monkeys (Nasalis larvatus), the Irrawaddy Dolphin (Orcaella brevirostris) and wild Banteng (Bos javanicus) still occur in significant numbers, and three species of crocodiles (Crocodylus porosus, Crocodylus siamensis and Tomistoma schlegeli) are also found in marshes in the Middle Mahakam Area. Conservation issues and threats • Lack of Regulation None of the Major Lakes or Major Rivers identified in this report has any form of protection by law. There was a proposal in 1981 to protect the Middle Mahakam Area as a nature reserve. However, the Indonesian Government rejected the proposition because of the high density of people already living there at that time (Scott 1989). Momberg et al. (1998), cognizant of the fact that the Middle Mahakam Area supported a large human population and an important fishery, recommended that “the area be given a Special Area status and a suite of policies and activities be enacted to maintain the ecological integrity and biodiversity of the area”. Despite the lack of current protection mechnisms, there are nearby protected areas that could be expanded to include the important lakes. Northeast of Lake Semayang lies the Muara Kaman, a strict nature reserve or cagar alam. This area of 62,500 hectares was designated to protect a vast swamp area. Also, Batu Bunbuna, a 450ha reserve that was established in 1927 close to Muara Muntai (Rosenthal & Baum 1980). • Commercial Animal Trade Fauna collected from the Mahakam lakes and its vicinity is considered by Suryadiptra et al. (2000) as one of the most significant threats to the biodiversity of the region. A recent (2000) field survey carried out by Wetlands International Indonesian Program discovered at least 23 rare fauna species (i.e., 2 Crocodiles, 7 turtles & tortoises, 3 snakes, 2 lizards, 5 mammals - including Mouse Deer and Barking Deer- and 4 bird species) being traded in the Muara Muntai area, both as live animals and animal skins. 52
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Ecoregional Assessment of Biological Diversity in East Kalimantan

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